Graphene is an allotrope of carbon with a structure of one-atom-thick planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. Because of its high conductivity, thermal stability, mechanical strength, and special quantum characteristics, graphene is considered to be an alternative to silicon in the future. Methods for producing graphene include mechanical peeling methods, chemical vapor deposition methods, and chemical reduction methods. Because it is simple and easy for mass production, chemical reduction methods are often used. A basic process of a chemical reduction method includes oxidation of the graphite powder into graphite oxide powder, peeling of the graphite oxide powder in a solvent to form graphene oxide, and reduction of the graphene oxide into graphene. The reducing agent is a key factor of the chemical reduction method. Some common reducing agents for graphene preparation are hydrazine, hydrazine hydrate, hydrazine derivatives, ethylenediamine, amino acids, sodium boron hydride, vitamin C, phenolphthalein, and the like.
Lithium-sulfur batteries have attracted much attention for their high-energy secondary green chemical power in recent years.